π‑Extended Thiadiazoles Fused with Thienopyrrole or Indole Moieties: Synthesis, Structures, and Properties

We report the syntheses, structures, photophysical properties,
and redox characteristics of donor–acceptor-fused π-systems,
namely π-extended thiadiazoles 1–5 fused with thienopyrrole or indole moieties. They were synthesized
by the Stille coupling reactions followed by the PPh3-mediated
reductive cyclizations as key steps. X-Ray crystallographic studies
showed that isomeric 1b and 2b form significantly
different packing from each other, and 1a and 4a afford supramolecular networks via multiple hydrogen bonding with
water molecules. Thienopyrrole-fused compounds 1b and 2b displayed bathochromically shifted intramolecular charge-transfer
(CT) bands and low oxidation potentials as compared to indole-fused
analog 3b and showed moderate to good fluorescence quantum
yields (Φf) up to 0.73. In 3b–5b, the introduction of electron-donating substituents in
the indole moieties substantially shifts the intramolecular CT absorption
maxima bathochromically and leads to the elevation of the HOMO levels.
The Φf values of 3–5 (0.04–0.50) were found to be significantly dependent on the
substituents in the indole moieties. The OFET properties with 1b and 2b as an active layer were also disclosed.

本报告详述了供体-受体共轭π系统的合成、结构、光物理性质及氧化还原特性的研究进展，具体涉及π-扩展的噻二唑1-5与噻吩并吡咯或吲哚基团共轭的结构。这些化合物的合成主要依赖于Stille偶联反应，并辅以PPh3介导的还原环化反应作为关键步骤。X射线晶体学研究表明，异构体1b和2b的分子堆积方式彼此显著不同，而1a和4a则通过与水分子形成多重氢键构建了超分子网络。相较于吲哚共轭的类似物3b，噻吩并吡咯共轭的化合物1b和2b展现出蓝移的分子内电荷转移（CT）带和较低的氧化电位，并表现出中等到良好的荧光量子产率（Φf）高达0.73。在3b-5b中，吲哚基团中引入的给电子取代基显著蓝移了分子内CT吸收的最大值，并提高了最高占据分子轨道（HOMO）能级。3-5的Φf值（0.04-0.50）被发现与吲哚基团中的取代基有显著依赖关系。此外，以1b和2b作为活性层的有机场效应晶体管（OFET）特性亦被揭示。